check_can_unlock_door

    This trigger will fire when an entity attempts to unlock a door or
    container. If the script deems that entity cannot unlock the door then it
    should present a message and return false. Since a return value is
    required, it is important to wrap the script in a protected block to
    ensure it runs to completion. The following variables are of interest for
    this trigger:

    @actor      - A pointer to the entity that is trying to unlock the door.

    @target     - A pointer to the target of the unlock action. This may be
                  an exit or an item.

    @direction  - If the @target is an exit, then this will be set to the
                  direction of the exit with respect to the room.

    @tool       - A pointer to an object that aided in the unlock action. For
                  instance when using a key to open a door, then this would
                  be a pointer to the associated key item.

    Your script must return a 1 or a 0 (or equivalent). Any value that does
    not evaluate to true, will prevent the @actor from completing the unlock
    action.